Mir-BFT: High-Throughput Robust BFT for Decentralized Networks

TL;DR

Mir-BFT is a high-throughput Byzantine fault-tolerant protocol designed for decentralized networks, enabling parallel leaders and signature verification sharding to significantly increase transaction processing rates on WANs.

Contribution

It introduces parallel leaders with request hash space partitioning and signature verification sharding, enhancing throughput and robustness in BFT protocols for decentralized systems.

Findings

Achieves over 60,000 signed transactions per second on a 100-node WAN

Outperforms state-of-the-art BFT protocols in throughput

Demonstrates robustness under various fault conditions

Abstract

This paper presents Mir-BFT, a robust Byzantine fault-tolerant (BFT) total order broadcast protocol aimed at maximizing throughput on wide-area networks (WANs), targeting deployments in decentralized networks, such as permissioned and Proof-of-Stake permissionless blockchain systems. Mir-BFT is the first BFT protocol that allows multiple leaders to propose request batches independently (i.e., parallel leaders), in a way that precludes request duplication attacks by malicious (Byzantine) clients, by rotating the assignment of a partitioned request hash space to leaders. As this mechanism removes a single-leader bandwidth bottleneck and exposes a computation bottleneck related to authenticating clients even on a WAN, our protocol further boosts throughput using a client signature verification sharding optimization. Our evaluation shows that Mir-BFT outperforms state-of-the-art and orders more than 60000 signed Bitcoin-sized (500-byte) transactions per second on a widely distributed 100 nodes, 1 Gbps WAN setup, with typical latencies of few seconds. We also evaluate Mir-BFT under different crash and Byzantine faults, demonstrating its performance robustness. Mir-BFT relies on classical BFT protocol constructs, which simplifies reasoning about its correctness. Specifically, Mir-BFT is a generalization of the celebrated and scrutinized PBFT protocol. In a nutshell, Mir-BFT follows PBFT "safety-wise", with changes needed to accommodate novel features restricted to PBFT liveness.